The invention relates to a grinding tool that comprises at least two parts.
Grinding tools in which a plurality of grinding wheels, in particular also grinding wheels with different thicknesses, are secured together into one grinding wheel packet are known for instance from DE 41 03 090 C1. Such grinding wheel packets are used in particular when contours are to be ground, whereby the contours are then put together using a corresponding packet that is adapted overall to the contour to be ground and that has corresponding partially profiled individual grinding wheels. The width to be ground can also be directly influenced by adding or removing individual grinding wheels from the grinding wheel packet. However, this is always associated with substantial equipment refitting complexity. If grinding is to be performed using such a grinding wheel packet for instance on a circumferential area and simultaneously on one or a plurality of planar shoulders, the problem occurs that the cutting volume from the grinding wheel on the sides of the packet with which planar grinding is conducted is substantially greater than for the circumferential grinding. This occurs because during circumferential grinding at least theoretically the grinding wheel has only a linear contact with the workpiece to be ground, while on the planar surfaces there is surface contact between the grinding wheel and the workpiece with a width equal to the amount at the planar shoulder due to the plunging process.
Due to the engagement of the grinding wheel with the planar surfaces, the wear on the grinding wheel in these areas as a rule is greater than on the circumferential area of the grinding wheel and/or a grinding wheel packet.
Compared to an individual grinding wheel, such a grinding wheel packet has the advantage that when there is rapidly occurring wear on the lateral wheels of the grinding wheel packet, only the latter have to be exchanged. However, this is associated with a high degree of refitting complexity and thus a substantially longer overall cycle period.
When grinding bearing bushes, for instance, which as a rule are ground using a plunge-grinding method, the actual bearing area, i.e. the circumferential area, is ground at the same time as the lateral shoulders and/or planar surfaces. Thus in the case of a grinding wheel that grinds such bearing areas, both the circumferential area and a lateral area of the grinding wheel are in contact with the surfaces to be ground. In this case, as well, the problem described in the foregoing occurs in that the lateral areas wear more rapidly than the circumferential surface. Although the grinding wheels can be dressed, normally such grinding wheels are not dressed on the planar side, but rather only on the circumference (see FIG. 8a: example of a lateral radius on the grinding wheel). However, if the normal dressing amount was also dressed on the sides, this would lead to a situation in which after dressing the tolerance width of a few μm or hundredths of a millimeter, which are required for the width of such bearing bushes, can no longer be maintained if this bearing bush is to be further manufactured using plunge-grinding. In the case of grinding wheels that have already been dressed, it is necessary to laterally offset the grinding wheel to the workpiece or vice versa so that both planar shoulders have to be ground separately, which means longer grinding time. On the other hand, if there is no dressing in the lateral areas, a shape error occurs with respect to the target contour of the grinding wheel.
In order to avoid these problems, during grinding of bearing bushes with planar shoulders using the plunge-grinding method it would be necessary to completely exchange a grinding wheel provided therefor with a grinding area in the circumferential area and with one or two grinding areas on its lateral surfaces more frequently in order to be able to attain the shortest possible grinding times.
However, the total costs for the grinding method are then highly impacted because of the relatively expensive grinding wheels.
In many grinding tasks today, grinding wheels with CBN, diamond, or comparable grinding means (hereinafter “CBN/DIA”) layers are used. These CBN/DIA grinding wheels in fact do attain significantly longer service life than conventional grinding wheels. However, planar-side dressing required for these CBN/DIA grinding wheels also leads to a reduction in the width of the grinding wheel and thus in the width of the bearing bush deviating from the specified target value when the plunge-grinding method is used without laterally offsetting the grinding wheel or the workpiece. The grinding process is not an actual true plunge method when there is such a lateral relative movement between workpiece and tool. Instead, the planar shoulders are ground successively in the bearing area to be ground. This again results in substantially higher processing times and costs.
In contrast thereto, it is the object of the invention to create a grinding tool with which actual dimensional tolerances or changes in the width to be ground can be compensated or are possible without partially or completely exchanging the grinding tool. In particular, a grinding tool is to be created that grinds on a plurality of contact surfaces simultaneously, in particular using plunge-grinding, and with which processing-related wear, and thus associated actual tolerances in the width of the grinding tool that would otherwise occur, can be compensated.